1.Circuit probably will work . Compare circuit with
micro's datashhet about VCC,VPP,EA,ALE,PSEN control.
Note - all producers change production lines. Don't
think this programmer to be Your '51 programmer forever.

You can build programmer on universal pcb and try. Instead ZIF
You can use standard 40pin sockets - solder one base, and
change regularily second (over first).

Better choice is to use some micros with ISP (AT89S52).
I love Winbond w78e516b - first time You need parallel programming for Your bootloader, after this - ISP is trough uart.


2.MAX232 is ok (with capacitors).
For prototype You can use transistors (1npn RX,1pnp+2npn TX) - allmost any computer will work with 0-5V instead true RS232 levels.