Definitions:
    Library: The software under this "CONTRIBUTING" root file. This excludes existing third-party source code vendored into the Library (often found under a "Vendor", "ThirdParty", or "Third-Party" directory)
    Author: The original developer OR exclusive rights holder of the Library
    Contribution (noun): Any feedback, system or process design suggestions, software patch files, pull-requests, or derived works provided to the Authors for inclusion into the Library
    Contributing (verb): To offer, explicily or implicitly, informally or formally, a Contribution on the *.reece.sx websites, any social media network, or via other communication mediums
    Source Provider: Any GIT (the software) based software source sharing service. Should the GIT tooling fall out of favour with the software development community, this may be substituted for any popular Source Version Control Software.
    License: The license provided to the general public for accessing and using the software Library (often found under the root ./LICENSE or ./COPYING file)
    Source Code: The software source code of the Library or the software source code derived from a Contribution
    You: A contributor of a Contribution

Terms:
    By Contributing to the Library, You:
        1) ...will have the right to access to Your Contribution in the form of Source Code and the Library's Source Code in its' current state at the time of Contributing, via a freely accessible Source Provider as deemed appropriate by the Author, under the conditions of the License,
        2) ...waiver Your exclusive copyrights, patent rights, and any further intellectual property rights that may be introduced into law, as they pertain to your Contribution,
        3) ...grant the Author the non-exclusive, transferable, and nonretractable rights to sub-license, use, modify, lease, commercialize, trademark, or patent parts of or the whole entirety of the Contribution,
        4) ...understand for the sake of representing the Library works in a professional manner, the Author will claim authorship and/or copyrights to the Contribution, without impeding on the rights granted to You by the first term. 
              For instance:
               * copyright informational headers/footers may or may not bundle the rights of the contributors to a single Author for sake of simplicity over verbosity,
               * future redistributions may not mandate every single contributor to be listed by name for attribution,
               * future licensing agreements / support contracts / related legal work need-not reference or involve You.
              You will, however, be able to still access your Contribution in the form of merged Source Code on the publicly accessible Source Provider under the License as laid out in the first term.
              To this extent, your Contribution history will not be lost, will not be intentionally removed from the public space, or be licensed to the general public under exclusive terms worse than the License at time of contributing.

Legal tl;dr/plain English intention:
    If you provide the author your changes, the author will license it back to you under the original license, while reserving the right to do whatever they please to their project.
    The sentiment of open source code sharing is respected by the authors commitment to keep your contributions available to you via a source control service under the original permissive license.
    Just don't expect a lifetime of attribution over insubstantial efforts; and don't expect the Author to be held hostage to a community of minority stake.