You can download free complete development software packages from
Lattice, Altera, Atmel, and certainly others like Xilinx.
You must send the identification number of one of your hard disks.
By e-mail, they return you a key for use of the software.

The Altera package contains a VHDL compiler, far better than PALASM
for complex state-machines descriptions (this is like Pascal or C, versus
Pentium assembler !) You obtain a JEDEC file understanded by all PAL
programmers. This is a fine software.

A project for building a PAL/GAL programmer can be found in the
collection of the Dutch review Elektor (ten years ago, approximately).
I doubt of interest to build your own programmer. The task is not
very hard, you must send a synchronous bit stream of programmation
information in the correct pin). The cost of time for building is certainly
higher than price of an of the shelf product.

Cheap programmers exist commercialy and ISP chips are programmable
directly in our system by a serial JTAG link (4 wires).

Best regards,
J. M.