This  software  may be freely used and distributed provided that this
copyright notice is left intact, and provided that:

     (1) The source code in machine readable form is provided with any binary
distribution, or made available at no additional cost to the recipients of the
binary distribution.
     (2) A binary version of a derivative work may be sold for a easonable
distribution charge (less than $50), and the source code in machine readable
form must be made available.
     (3) A derivative work may not impose and restriction on the free
distribution of the source code.