I started four days ago to write a library of skinnable controls for lazarus, this library uses some units or class from the library SpTBXLib and not ported but modified, I had to change the names and a lot of things in these files to make it portable and to make them compatible with the rest of names of the library, I want whether I can distribute this library, the licenses I do not understand 
here's SpTBXLib license:
http://www.silverpointdevelopment.com/sptbxlib/SpTBXLib-LICENSE.htm
Is what I can publish the source and what should I do?
From that: no, it is proprietary:
1. Registration (payment) of the Software is required, such payment is made
to the Author of the Software.
and redistribution of modified content is explicitely forbidden:
3. All redistributions of the Software's files must be in their original,
unmodified form. Distributions of modified versions of the files is not
permitted without express written permission of the Author.
Next time, look at the license before using it.