Projects that rely on BOSL exceptions should say that they do

[daira]

This is important licensing information since it affects how those projects can be forked. The following librustzcash crates and components depend on orchard:

• zcash_primitives:

  librustzcash/zcash_client_backend/Cargo.toml

  Line 27 in 8ad60a0

  orchard = "0.2"

• zcash_client_backend: via zcash_primitives (also used by zcash_note_encryption and zcash_proofs)

  librustzcash/zcash_client_backend/Cargo.toml

  Lines 38 to 39 in 8ad60a0

  	zcash_note_encryption = { version = "0.1", path = "../components/zcash_note_encryption" }
  	zcash_primitives = { version = "0.7", path = "../zcash_primitives" }

• zcash_client_sqlite: via zcash_client_backend and zcash_primitives

  librustzcash/zcash_client_sqlite/Cargo.toml

  Lines 26 to 27 in 8ad60a0

  	zcash_client_backend = { version = "0.5", path = "../zcash_client_backend" }
  	zcash_primitives = { version = "0.7", path = "../zcash_primitives" }

• zcash_proofs: via zcash_primitives

  librustzcash/zcash_proofs/Cargo.toml

  Line 31 in 8ad60a0

  zcash_primitives = { version = "0.7", path = "../zcash_primitives" }

• zcash_extensions: via zcash_proofs

  librustzcash/zcash_extensions/Cargo.toml

  Line 19 in 8ad60a0

  zcash_proofs = { version = "0.7", path = "../zcash_proofs" }

• zcash_note_encryption: via zcash_primitives

  librustzcash/components/zcash_note_encryption/Cargo.toml

  Line 28 in 8ad60a0

  zcash_primitives = { version = "0.7", path = "../../zcash_primitives" }

A copy of the notice is needed for each potentially reusable crate or component.

Suggested wording is:

Downstream code forks should note that the code in this repository depends on
the 'orchard' crate, which is licensed under the Bootstrap Open Source License.
A license exception is provided allowing some derived works that are linked or
combined with the 'orchard' crate to be copied or distributed under the original
licenses (in this case MIT / Apache 2.0), provided that the included portions of
the 'orchard' code remain subject to BOSL.
See https://github.com/zcash/orchard/blob/main/COPYING for details of which
derived works can make use of this exception.

See also:

• https://forum.zcashcommunity.com/t/bosl-or-mit-orchard/41439/118
• Projects that rely on BOSL exceptions should say that they do zcash#5931 (similar issue for zcashd)
• Projects that rely on BOSL exceptions should say that they do #577 (PR for librustzcash)