For all you legal/tax experts...
Here's a bit from the California sales tax code. I'll translate for you; except for certain circumstances (none of which include software), leases are treated as sales for tax purposes.
LEASES AS SALES OR PURCHASES.
(1) IN GENERAL. Any lease of tangible personal property in any manner whatsoever for a consideration is a “sale” as defined in section 6006 of the Revenue and Taxation Code, and a “purchase” as defined in section 6010 of the Revenue and Taxation Code, except a lease of:
(A) Motion picture films and video tapes, including television films and video tapes, whether or not they are productions complete in themselves. See, however, subdivision (d)(2) below for application of tax for periods on and after September 1, 1983, to leases of video cassettes, videotapes, and videodiscs for private use under which the lessee or renter does not obtain or acquire the right to license, broadcast, exhibit, or reproduce the video cassette, videotape, or videodisc.
(B) Linen supplies and similar articles, including such items as towels, uniforms, coveralls, shop coats, dust cloths, caps and gowns, etc., when an essential part of the lease is the furnishing of the recurring service of laundering or cleaning of the articles leased.
(C) Household furnishings with a lease of the living quarters in which they are to be used. The lessor of the household furnishings must also be the lessor of the living quarters. The living quarters must be real property rather than tangible personal property.
(D) Mobile transportation equipment for use in transportation of persons or property (see Regulation 1661 (18 CCR 1661)).
(E) Tangible personal property leased in substantially the same form as acquired by the lessor or leased in substantially the same form as acquired by a transferor as to which the lessor or his or her transferor acquired the property in a transaction that was a retail sale with respect to which the lessor or the transferor has paid sales tax reimbursement or as to which the lessor or the transferor has timely paid use tax measured by the purchase price of the property.