It's safe for everyone but the people who make 8051 programmers.

There is one major differecnce with the PHILIPS part, it will run at 6 clocks per cycle instead of 12. If your software can tolerate running twice as fast, you are ok. The chip can be changed to 12 clocks per cycle, but this requires a device programmer.

Otherwise, I recommend ATMEL T89C51RD2 or relatives. The 6/12 clocks per cycle is SFR programmable, and the default is 12.

You also must make sure that P2.6 and P2.7 are not pulled low during reset, or you will not be able to enter ISP mode.