To get access to POWER8/9 literature you sign away your rights to OPEN-POWER. Also if you make anything for POWER8/9, under a public license (what license you can/can't use are dictated by the license agreement), using docs obtained from an OPEN-POWER member company if that member company upon leaving the OPEN-POWER may claim ownership of your code.
They'll really only let you use 3 Clause BSD or Apache2. Linux has the only exception for GPLv2, and GPLv3 is banned, using it on a project can have your membership to OPEN-POWER revoked, and your code ownership transferred to IBM. If they decide to purpose it.
OPEN-POWER isn't open. The docs are free and if you write anything too useful a high paying member can seize your software. The only protection from this, is to buy in as a high level enterprise member. OPEN-POWER is down right predatory for research free-tier membership.