This message was posted on behalf of Intel Corporation
Thanks for reaching out!
May I ask why you are using the image ww18-05?
Using the latest image (201606081705) I simply used the command opkg install opencv-dev and after installing its dependencies (which are a lot), it installs the package correctly without any issue.
If there is no major reason why you need to use the image ww18-15, I suggest you to install the latest (which you can download from https://software.intel.com/en-us/iot/hardware/edison/downloads) image and try again.
If you must use the image ww18-15, please let me know and I'll install it on my Edison to see if I can replicate the issue and if so, try to see how to resolve it.
I hope this information helps you,