What does this mean?

"Neither party to this agreement may assign, sell or transfer any part thereof to any other firm or entity without first obtaining the written permission of the other party hereto."

For the guy receiving the work, does that mean, I can't resell my own script without permission from the programmer?

It could be an Exclusive contract... in an exclusive contract, you cannot resell the same thing on other websites. Of course, you can sell on that same site, and may be you will get more commission. This is not an exclusive legal advice though. If he's a programmer for you, then he may be expecting a share (life-long) for being holder of the copyright/s for his creativity ... change the programmer in that case and get the new one to sign a proper contract without the ridiculous clauses, IMHO.

This is poorly written, even for legalese. If this is a contract you're working up with someone else (as it seems to be), I would suggest having this line cleaned up a bit.

But yeah, it sounds like what srb888 is saying sounds about right.

neither party can sell on their share of the contract to a third party without the other parties agreement - as such it is a way to lock in both parties or for security a default breach of contract if one does pass on or sell.

It is normally used as a collective catch all line for the whole contract unless in a specific section of the agreement.