I don't have any scripts running.
That is why other people can grab stuff. ULib and ULX don't include prop protection.
You can get one from Facepunch forums (or search Garrysmod.org, which many links from Facepunch link to)
Many of our users recommend SimplePropProtect. It's mostly compatible. Jay###some_numbers### just posted a file that supposedly fixes the jail escape issue too.
Search our forum for that fix.
Also, there is a green ring in the middle of the prop and no one can grab the prop anywhere else than there.
As Zakap mentions above, you need the models on the server. If you don't have the actual models, then only you and other players that have that same model can 'see' it, but not interact/physically touch it other than the green ring.
Besides Garry's mod, I recommend installing CounterStrike:Source, HL2MP (which I think gets installed along with Gmod), and DOD:Source.
See your hosts help for assistance on how to install those model/servers.