WRT54G; What is latest version of firmware ?

Question

I have a WRT54G v4 and somehow I had noticed I upgraded to 4.30.5.  When I went to web to see if I still ahd latest it said 4.21.1 was latest.  So, I quickly re-flashed with 4.21.1.  I went into the 4.30.5 release notes (below) and it DOES say WRT54G.  What's up ?
Linksys, A division of Cisco Systems, Inc.
Product:                WRT54G
Classification:         Firmware Release History
Firmware  Date:  04/27/2006
Release Date:           05/25/2006
Last Firmware Version: 4.30.5
Firmware 4.30.5
- Resolves UPnP vulnerability reported by SANE
Firmware 4.30.2
- Resolves issue with filter name
- Resolves issue where service name for PPPoE cannot be added
- Resolves issue with detecting UHP modems
- Resolves issue where DynDNS Custom and Static accounts cannot be used
- Resolves issue with WEP passphrase not recognizing spaces
Firmware 4.20.7
- Resolved issue with SecureEasySetup button delay
- Resolved issue with SecureEasySetup overwritting current wireless settings
- Resolved issue with not being able to disable SecureEasySetup button
- Resolved issue with Diag light being constantly lit after upgrading to 4.20.6 on v.1 hardware
- Resolved issue with iDefense security vulnerability
- Resolved issue with L2TP disconnect
- Resolved issue with SecureEastsetup long button push not resetting wireless settings
Firmware 4.20.6
- Resolve issues with setup wizard
- Updated wireless security menu
- Resolve issues with port based QoS
Firmware 4.00.7
- Adds SecureEasySetup push button support
- Resolves large file transfer issues
- Resolves issue with enabling TKIP after enabling WEP
- Updated QoS features
- Resolves issues with multiple Access Restrictions policies
- Resolves issue where multicast breaks when MAC filter status changes
Firmware 3.03.6
- Supports hardware version 3
- Updated help file
Firmware 3.03.1
- Wi-Fi certified
Firmware 3.01.3
- Updated wireless driver
- Supports hardware version 2.2 (cannot downgrade to previous versions)
- Resolves issue with VoIP adapters
- Resolves issue with long domain names
Firmware 2.04.4
- Updated wireless driver
- Updated certificate generation for https access
Firmware 2.04.3
- Resolves issue with disabling firewall
- Added QoS function
- Added Port Triggering function
- Added L2TP option for WAN connection type
- Added ability to back up and restore configuration files
- Added Wireless isolation function
- Added ability to filter internal NAT redirection
- Added ability to restrict access to web GUI from wireless clients
- Added ability to filter IDENT port 113
- Resolves issue with HeartBeat WAN connection
- Added support for 40/56bit cipher to support old browsers to use https
- Resolves issue with PPTP passthrough
- Changed WPA Group Key renewal time range to 600~7200 seconds
- Added IGMP proxy support
- Added ability to allow web GUI access only through https or http
Firmware 2.02.2
- Updated wireless driver to support all versions of WRT54G hardware
- Adds support to allow WAP54G connect as a repeater
- CTS protection mode set to disable by default to improve wireless performance in normal environments
- Resolved issue where the WLAN LED stays on even when wireless is disabled
- Resolved security vulnerability causing the web server in the router to crash
Firmware 2.00.8 (WRT54G v.2 only)
- Updated wireless driver
Firmware Version 1.42.2
- Updated wireless driver to 3.31.15
- Added URL and contents filters
- Added L2TP passthrough
- Added HeartBeat Signal support
- Resolved issue with Connect on Demand
Firmware Version 1.41.2
- Updated GUI format and layout
Firmware Version 1.30.7
- Adds UI control to enable/disable frame bursting
- Resolves issue with firmware upgrade error in Internet Explorer 6.0.2800.1106.xpsp2.030422-1633, on Windows XP pro.
- Send 192.168.1.1 to disable DynDNS
- Resolves issue with using the 4th tx key for WEP
- Resolves issue with disconnecting PPPoE causing WPA to be disabled
Firmware Version 1.30.1
- Adjust PPTP max MTU value from 1400 to 1460
- The router is now certifiable for the UPnP logo
- Complies with final 802.11g standard
- Improved performance asymmetry between the transmit and receive paths
- Receive Broadcast packets from renew state. Some DHCP server (Dlink 300G+) send broadcast ACK after it receives a REQUEST
- Fix: The firmware upgrade will fail, if DDNS updates while upgrading
- Fix: If first DNS address fails, the second or third DNS address will be used to resolve domain names
- Added the following items under Setup Page: 
    - Router Name
    - Manual Time Server
    - MAC Clone
    - wireless domain
    - Security Settings
- Added the following items under System Page
    - UPnP enable/disable
    - Ping Test and Traceroute
- Added the following items under Wireless Page
    - CTS Protection Mode
    - Basic Rate
- Added the following items under Status Page
    - Router Name
    - Start IP Address
    - End IP Address
- Added Wi-Fi Protected Access(TM) support including AES and TKIP encryption
- Resolves issue with Port Forwarding name showing up as garbage characters
- Added "B-Only" option to wireless modes
- Added "Default" option to Basic Rate settings
Firmware Version 1.02.1
- Incorporates updates found in the Draft IEEE 802.11g version 6.1 specification
- Resolves interoperability issues with legacy 802.11b devices under Mixed Mode
- Resolves a performance bug where the performance in a mixed b, g network did not go up once the last b client disassociated
- Resolves issue where WEP degrades performance
- Resolves issue with TZO DDNS Service
- "Domain Name" replaces "name"
- TFTP server will only verify image file name "xxxx.bin"
- MAC Address Filter under the Advanced tab works on both wired and wireless clients
- Fixed a bug that prevented wireless clients from connecting to the Internet if there was no active wired PC (PPoE customers in Europe and China only)
- Support for UPnP enabled applications such as MSN Messenger
- Fixed a bug that caused computers connected to the LAN ports to be dropped at some interval only to be immediately re-connected
- Fixed Dynamic Routing issue between 2 Routers
- Allows User to name Static Route Configurations
- Modified PC List Web Page to avoid confusion
- Stabilized Wireless-G to LAN and WAN Throughput
- Stabilized Wireless-B to LAN and WAN Throughput
- Improved LAN-WAN Throughput
Firmware Ver.: 1.01
- Initial release

Answer 1

History.
Linksys released the 4.30 firmwares for the WRT54GL model which are compatible with the WRT54Gv1-v4.
I guess some people were confused to see WRT54GL on the web interface of the router although they had a WRT54G.
Thus they re-released the firmware for the WRT54Gv1-v4 with 4.21.* showing the correct model name.
You should be able to use either firmware for either router. If you check the release notes of 4.21.* and 4.30.* you'll notice that they basically have the identical history of changes. 4.30 is now a little bit more advanced if you look on the WRT54GL downloads page.