As predicted, the open-source community has come up with a way to convert VxWorks-based Linksys wireless WRT54G routers to Linux. The process does not require hardware hacking and installs a recent version of "DD-WRT micro."
A version of Linux that supports the VxWorks-based "series 5" WRT54G has been available since April, when the DD-WRT project created its "micro" edition, with a 1.7MB footprint. However, the firmware could only be installed on routers modified to expose their JTAG ports (complicated instructions here).
Now, Jeremy Collake, aka "db90h," appears to have created a "VxWorks Killer" flash image that overwrites the VxWorks bootloader on series 5 WRT54G routers with normal Broadcom CFE firmware. This then enables the device to be put into maintenance mode at startup, after which Linux firmware can be installed easily.
Currently, the process is not reversible on WRT54G devices that have not been modified to add a JTAG interface. Additionally, power failure during the two-second installation process could permanently incapacitate or "brick" the device.
Compared to the full DD-WRT distribution, the "micro" version leaves out packages that include chillispot, nocat, rflow, kaid, samba client, SNMP, IPv6, MMC/SD Card Support, SSH, PPTP/PPTP Client, and UPnP, according to Wikipedia. However, it does support PPPoE.