How can I program GALs on a shoestring budget?
For hobbyists the problem with GALs has been lack of programming documentation. Chip manufacturers have kept the algorithms a closely guarded secret and only released the information to manufacturers of 'approved' device programmers. This is understandable because the chips can be tricky to program and manufacturers want to ensure that it is done properly. The little information that is publicly available has come from a few old datasheets and reverse engineering. 

Apart from GALblast and my ATFblast a few other DIY programmers have appeared over the years - including one by ChaN, an article in the May 1992 edition of Elektor magazine, and shareware projects for the Commodore Amiga and ZX Spectrum. Some of these include source code. But be warned - to fully understand the programming algorithms you will need to study it carefully.  

A GAL is put into program verify mode by applying 12V to the 'edit' pin, but for actual programming it requires a higher voltage that varies depending on the manufacturer, type, and chip revision. Most GALs have pre-programmed bits that can be read out to tell the device programmer what voltage and timing to use. 

Atmel's 'ATF' PLDs are the exception - they can be programmed and verified at 12V, and they don't have any bits to tell you what settings are required. Unfortunately the ATF22V10C has a different programming algorithm which is not supported by GALblast, and the lack of config bits causes GALblast to fail on the ATF16V8 and ATF20V8 too.  

GALblast is probably your best bet for programming older GALs, provided that you can find a PC with a parallel port or install a PCI parallel port card. One slight problem is that the 16bit software doesn't work in Windows XP or later due to trying to access the printer port directly. Marinov Georgiy has has modified the software to work through a device driver. His version can be downloaded from here (I hope to incorporate his changes into my own ATFblast program soon).            

If a parallel port is not available then you could port the software to a microcontroller board such as the Arduino Nano, and talk to it via the USB-serial port. I am currently working on a project which does just that (so far I have gotten it to read GAL and ATF chips, but haven't tried programming them yet). If you restrict the selection to ATF then you only need 5V and 12V. the 12V supply can be produced from 5V with a small boost regulator.  

Advantages of ATF PLDs over other GALs include the single 12V programming voltage, that they are still in production, and the 'zero-power' variants draw much less static current (less than 1mA vs up to 130mA for a GAL22V10).