sigrok-firmware-fx2lafw include includes a bundled copy of fx2lib. These are
8051 hardware bits, and would be incredibly cumbersome to ship as different
packages.

As upstream explains:
"We want a local fx2lib copy in fx2lafw for various reasons, e.g. to make
life simpler for all distros (none of which ship any fx2lib packages,
and neither would it make sense to do so really), and as we'll want/need
local changes to fix build issues and possibly other stuff anyway."

Has the library behaviour been modified? If so, how has it been modified? If the library has been modified in ways that change the API or behaviour then there may be a case for copying. Note that fixing bugs is not grounds to copy. If the library has not been modified (ie: it can be used verbatim in the distro) there's little chance of an exception.
The library was not modified in a significant way.

Why haven't the changes been pushed to the upstream library?
Upstream has been inactive for almost two years. Only recently has upstream
showed some activity.

Have the changes been proposed to the Fedora package maintainer for the library?
The library is not packaged in Fedora.

Could we make the forked version the canonical version within Fedora? For instance, if upstream for the library is dead, is the package we're working on that bundles willing to make their fork a library that others can link against?
The package we're working on upstream is not willing to maintain the library
beyond strictly the porposes of maintaining fx2lafw.

Are the changes useful to consumers other than the bundling application?
No. the changes only relate

Is upstream keeping the base library updated or are they continuously one or more versions behind the latest upstream release?
Upstream is keeping a slightly modified copy from a snapshot a few years old.

What is the attitude of upstream towards bundling? (Are they eager to remove the bundled version? are they engaged with the upstream for the library? Do they have a history of bundling? Are they argumentative?)
Upstream does not want to remove the bundled version, as this will create a
very worrying point of failure. Since we're talking about a firmware library,
any seemingly innocent changes to the library can break the fx2lafw firmware.
For example, an innocent change that causes a simple timing difference can break
the entire firmware. fx2lafw upstream has spent significant time testing the
firmware, and are not willing to make themselves vulnerable to such failures.

Please include any relevant documentation -- mailing list links, bug reports for upstream or the bundled library, etc.
upstream's page on fx2lafw: http://sigrok.org/wiki/Fx2lafw
fx2lafw git repo: http://sigrok.org/gitweb/?p=sigrok-firmware-fx2lafw.git;a=summary

upstream commit that imported the library, with an explanation of why a local
copy is the preferred way:
http://sigrok.org/gitweb/?p=sigrok-firmware-fx2lafw.git;a=commit;h=3608c1063d17c56c038434eba5a6b11f26e530b5
Fedora review request: https://bugzilla.redhat.com/show_bug.cgi?id=922246