Since the Shareware version of doom doesn't support loading of other iwads. If i were to compile my own doom using the source, and i had another iwad, would i be able to load this iwad(not shareware iwad, probably aliens tc or something), or would it block it like the shareware version?

If you have your own custom coded version of the source, you can make it do whatever you wish it to do.
Simply recompiling the source, will not prove any additional benefits if you do not inject your own code.

Note: the version of DOOM source you have, is the Linux version - I have a copy of it myself. They did not release the MAC and DOS versions, due to patent / copyright claims.

Thanks