The INSTALL file currently suggests that the 'pbcompile' & 'fasm' files should be copied from /usr/share/purebasic/compilers/ to /usr/bin.
Problem is that when the next update comes along in 6 months time, the 'pbcompiler' & 'fasm' files in /usr/bin may be incompatible with the rest of PB.
Its a better idea to link these files to avoid such incompatibilities:
1) Move the purebasic directory to /usr/share
$ mv ./purebasic /usr/share
2) Link the fasm & pbcompile files to /usr/bin
$ cd /usr/bin
$ ln -s /usr/share/purebasic/compilers/pbcompiler ./pbcompiler
$ ln -s /usr/share/purebasic/compilers/fasm ./fasm