Here is an Android 4.2.2 Jelly Bean rooted firmware for the PIPO M9 tablet (aka Max-M9, not the M9pro version) that should work on both the 3G and WiFI tablet models. It is based on latest PiPO update dated 2013/10/18 and offers the multi-windows feature.

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Build information: 

Kernel: Linux version 3.0.36+ (root@lzj-desktop) (gcc version 4.6.x-google 20120106 (prerelease) (GCC) ) #58 SMP PREEMPT Fri Oct 18 16:15:11 CST 2013

Android 4.2.2 JB: rk30sdk/rk30sdk/rk30sdk:4.2.2/JDQ39/eng.root.20131018.164926:eng/opinions-on-teclast-p90hdst-keys

ro.rksdk.version=RK31_ANDROID4.2.2-SDK-v1.04.0

Notes: 

- Certificate Center (will ask for product key) and PiPO launchers have been kept in the firmware 

Custom firmware features:

• root with latest SuperSU version 1.65 (free version)
• removed most Chinese and unnecessary applications
• Google Play Store fixes so more application are visible/compatible
• updated busybox v1.21.0.git (2012-11-29)
• Unix like init.d boot scripts support, more details on init.d scripts here
• changed permissions on external sdcard to allow write access
• increased space for applications (/data partition) to 4 GB
• NEW! kernel modules (cifs, tun, lan, serial, xpad) compiled by Oma & Crew RKTablets, thank guys!

Download: kasty-pipo-m9-422-105_20131018-rooted4.zip

Flash with Rockchip Batch Tool version 1.7, use Restore button.

Please report any problem with this firmware, I can't verify this custom firmware works as I don't have a PIPO M9 tablet to test the custom firmware.  

Thanks to sho25 for the tip