The problem with Self in the 1990s wasn't the lack of sources (I just checked the 1994 Self 4.0 sources and the license looks like the typical BSD one) but the fact that the binaries only ran on Sparc workstations and not the computers people actually had. I might as well post the whole text of the license:

# Sun-$Revision: 21.2 $

Copyright 1995 Sun Microsystems, Inc. and Stanford University.

All Rights Reserved. RESTRICTED RIGHTS LEGEND: Use, duplication, or disclosure by the government is subject to restrictions as set forth in subparagraph (c) (1) (ii) of the Rights in Technical Data and Computer Software Clause at DFARS 252.227-7013 (Oct. 1988) and FAR 52.227-19(c) (June 1987).

Sun Microsystems, Inc. 2550 Garcia Avenue Mountain View, CA 94043 USA

LICENSE:

You may use the software internally, modify it, make copies and distribute the software to third parties, including redistribution for profit, provided each copy of the software you make contains the copyright notice set forth above, the disclaimer below, and the authorship attribution below.

DISCLAIMER:

Sun Microsystems, Inc. makes no representations about the suitability of this software for any purpose. It is provided to you "AS IS", without express or implied warranties of any kind. Sun Microsystems, Inc. disclaims all implied warranties of merchantability, fitness for a particular purpose and non-infringement of third party rights. Sun Microsystems, Inc.'s liability for claims relating to the software shall be limited to the amount, if any of the fees paid by you for the software. In no event will Sun Microsystems, Inc. be liable for any special, indirect, incidental, consequential or punitive damages in connection with or arising out of this license (including loss of profits, use, data, or other economic advantage), however it arises, whether for breach of warranty or in tort, even if Sun Microsystems, Inc. has been advised of the possibility of such damage.

AUTHORSHIP:

This software has been derived from the Self system, which resulted from the combined efforts of:

Bay-Wei Chang, Craig Chambers, David Ungar, Elgin Lee, John Maloney, Lars Bak, Mario Wolczko, Ole Agesen, Ole Lehrmann Madsen, Randall B. Smith, and Urs Hoelzle.