You can find GNU GPL related source code below.
GWN: Click here to download
GXE502x: Click to Download
GXP2200: Click to Download
GXP11xx/GXP14xx/GXP21xx Series: Click to Download
GXP16XX Series: Click to Download
GXP17XX Series: Click to Download
GXP2130/2135/2140/2160/2170: Click to Download
GRP2612/2613/2614/2615/2616: Click to Download
GXV3140: Click to Download
GXV3175: Click to Download
GXV32xx: Click to Download
GXV3350: Click to Download
GXV3370: Click to Download
GXV3380: Click to Download
GAC2500: Click to Download
GVC32xx: Click to Download
GVC3220: Click to Download
DP71x: Click to Download
DP752/750/760/730/722/720: Click to Download
HT50x/GXW40xx Series: Click to Download
HT7xx Series: Click to Download
HT8xx Series: Click to Download
GXW42xx Series: Click to Download
GXW450x Series: Click to Download
Surveillance GXV36xx/GXV35xx Series: Click to Download
GDS3710: Click to Download
GDS3705: Click to Download
GSC3510/GSC3505: Click to Download
GSC3570: Click to Download
GSC3610/GSC3615: Click to Download
WP820: Click to Download
WP810: Click to Download

UCM6XXX Series:
- Boot_Kernel_UCM61XX_R1_0_11_27.zip
- Boot_Kernel_UCM62XX_UCM65XX_R1_0_11_27.zip
- 3rd_Party_Libraries_UCM6XXX_R1_0_11_27.zip
- Asterisk13_UCM6XXX_V1_0_11_27.zip
- DHADI_UCM6XXXX_R1_0_11_27.zip
- WebUI_UCM6XXX_V1_0_11_27.zip
- SVIP_UCM6XXX_1_0_11_27.zip