Is it difficult to get a proprietary software license? Why?

Software can either be copyrighted or patented, depending on what the software does. If you develop the software by yourself, you own all the rights to it yourself; if you are part of a group, everyone may have a claim to it. That's the "proprietary" part. A license is your (or the group's) permission to someone else to use your proprietary software. An intellectual property attorney can draft this document for you in a manner that will keep all the proprietary rights in your hands.

You create software - so you need a license agreement in order to permit others to use your software. Contact a licensing attorney to have the document prepared. Costs vary - depending upon the details of the agreement. Not difficult to obtain, but again, the cost will depend upon how much detail you want included in the agreement.