The SPL has the following features which distinguish it from other licenses:

  -- Allows consultants to sell closed-source software to their customers
     for limited end-user use, but does not allow mass market distribution
     of non-free works.

  -- Hands the community the power to take action against violators of 
     the license--even if the original author is not around, has lost 
     interest, or doesn't have the time or money. 

  -- Ensures that "improved" versions aren't encumbered by patents or by 
     dependence on non-free software that you would have to pay for.

  -- Requires that all other modifications be shared with the community,
     even if they aren't distributed. Thus you can't hide your improvements
     behind an application server.

  -- Transfers to the original author rights to alterations to the 
     original software itself (but not other derivations).

  -- Has a fairly strong requirement that credit be given to the original
     author on any derived work.

  -- Strong language to deal with third party claims, preventing you from
     being liable for negligence when someone who has NOT licensed the
     software is somehow harmed by it (eg: a user of some licensee).

  -- Protects CD distributors in the event of a license violation: they 
     won't have to recall CD's they've already pressed with the infringing
     software.


Potential problem spots that I can see: 

  -- Does the language giving distributors the right to take action 
     against violators give the distributors powers to change the license?

  -- Does the termination language allow someone who improved the software
     to later pull the plug by deciding to infringe? Then their improvement
     would no longer be available to the community?? But if you disallow 
     this then corrupted versions can become lawful by way of whatever 
     exception you write. Ugh.

  -- Is the definition of "depends on" adequate. I want the software to be
     usable on non-free platforms providing it doesn't gain extra
     functionality on those platforms that the free platforms don't get
 
  -- UCITA... are my acceptance terms realistic? Are my disclaimers still
     valid after UCITA? I don't know...

  -- I used to have a "ok to link with GPL" clause, but that also gives 
     people a route around my strong disclaimers. I'm also worried that 
     the GPL may not adequate defend against runtime linking issues and
     other things. For now I have left this clause out, but I would like
     to be compatible with the GPL... sigh. 

  -- The "YOU MAY USE OUR SOFTWARE.." section no longer offers the right
     to sublicense the software. The sections dealing with derivatives 
     explicitly declare the sublicensing conditions. I can't see this as
     a problem, but am I missing something?

  -- Does the "NON-FREE APPLICATIONS" section give recipients of 
     the non-free applications enough power to use the software?

  -- Do I need to include language specifically dealing with runtime
     and dynamic linking? I suppose I ought to.