sequent derivative works open up their own code base. For an evaluation of GPL's via-
bility under German law, see Axel Metzger and Till Jaeger, "Open Source Software and
German Copyright Law," _International_Review_of_Industrial_Property_&_Copyright_Law_
32 (2001):52.

[4-27] See http://www.fsf.org/copyleft/gpl.html.

[4-28] Stallman, 56.

[4-29] See Moody, 168 (describing open source definition).

[4-30] For a fuller discussion of various open code licenses and their implications, see
David McGowan, "Legal Implications of Open Source Software," _University_of_Illinois_
_Law_Review_ (2001): 101, 113-119; Patrick K. Bobko, "Can Copyright Keep 'Open
Source' Software Free?," _AIPLA_Quarterly_Journal_ 28 (2000): 81; Ira V. Heffan, "Note:
Copyleft: Licensing Collaborative Works in the Digital Age," _Stanford_Law_Review_ 49
(1997): 1487; Daniel B. Ravicher, "Facilitating Collaborative Software Develop-
ment: The Enforceability of Mass-Market Public Software Licenses," _Virginia_Journal_of_
_Law_&_Technology_ 5 (2000): 11.

[4-31] Wayner, 260.

[4-32] The latest operating system from Apple, OS X, includes a portion called Darwin
that is licensed under an open source license. See http://www.apple.com/macosx/tour/
darwin.html.

[4-33] For detailed analyses of this case, see Ken Auletta, _World_War_3.0:_Microsoft_and_Its_
_Enemies_ (New York: Random House, 2001); David Bank, _Breaking_Windows:_How_Bill_
_Gates_Fumbled_the_Future_of_Microsoft_ (New York: Free Press, 2001); John Heilemann,
_Pride_Before_the_Fall:_The_Trials_of_Bill_Gates_and_the_End_of_the_Microsoft_Era_ (New York:
HarperCollins, 2001).

[4-34] The government isn't the only one to make this allegation. As Red Hat chairman
Bob Young describes it, "Microsoft appeared to have gone so far as to dictate how fast
other companies could bring out new products -- or if they could bring them out at all,
for that matter." Young and Rohm, 7.

[4-35] Some attempts were made at graphical user interface desktop environments before
Windows hit pay dirt, including VisiOn (by VisiCalc), Top View (by IBM), GEM (by
Digital Research), and Interface Manager (Microsoft's precursor to Windows); none
fared well with consumers, however. Ceruzzi, 276.

[4-36] In a well-known story, the company didn't actually write DOS but simply licensed
it from Tim Paterson of Seattle Computer Products. Microsoft paid "about $15,000 for
the rights to use Seattle Computer Products's work." Microsoft later paid more for the
complete rights. Ibid., 270.

[4-37] Stan Miastkowski, "A Cure for What Ails DOS," _BYTE_ (August 1990): 107.

[4-38] See _Caldera_ v. _Microsoft,_ 72 F. Supp. 2d 1295, 1299 (D. Utah, 1999).

[4-39] Jim Carlton, _Apple:_The_Intrigue,_Egomania,_and_Business_Blunders_That_Toppled_
_an_American_Icon_ (New York: Times Books/Random House, 1997), 39-47.

[4-40] Ibid., 28.

[4-41] "Strategic behavior arises when two or more individuals interact and each indi-
vidual's decision turns on what that individual expects the others to do." Douglas G.
Baird, Robert H. Gertner, and Randal C. Picker, _Game_Theory_and_the_Law_ (Cam-
bridge, Mass.: Harvard University Press, 1994), 1. As I use the term, I mean to restrict it
to cases where the resulting behavior raises questions under antitrust law.

As David Bank writes, the notion of a competitive strategy to protect Microsoft's base
was at the core of Microsoft's product design. This was referred to within Microsoft as the
"strategy tax." As Bank writes:

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