IvToolkit is a shared-functionality framework used primarily in its author's own mods. Available for Forge on Minecraft 1.7.10–1.12.2, it offers source code under the Apache 2.0 license for inspection and integration. Modpack use is permitted with attribution: link to the mod and mention its author.
For a pack that uses IvToolkit, rent your own Minecraft server and install the framework with one click from the panel.