GIMP Version: 2.8.10
Operating System: Windows
OS Version: 8
GIMP Experience: Beginner Level

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I come from Photoshop where having an alpha channel (not a layer mask) doesn't make the image transparent, but in GIMP it does.

So how can I have an alpha channel that will be exported but at the same time is disabled so I can edit the RGB channels without making them invisible?

In Gimp, an alpha channel allows the image to be transparent, but doesn't make it transparent by default. You have to fill it with black/set it to all zeroes to achieve this (in general by editing a layer mask). What did you do exactly?

It's not exactly clear what you're asking, but...
If you open an image with Gimp that doesn't contain an alpha channel, (ie. a JPG Image, JPG images do not support transparency). Then you add an alpha channel to this image. Exporting this image in a format which supports an alpha channel such as, GIF, PNG, BMP/TGA, TIFF or Gimp's native file format of XCF. Will not cause the image to become "invisible" once exported.
If exported using any of the image file formats mentioned above. The image will retain the alpha channel information, (without causing the image to become "invisible" once exported), and can be once again opened with Gimp for editing in the "RGB" mode, and still retain it's alpha channel information.

On the other hand, if you're wishing to export an image and maintain a "Layer Mask", for editing later. You will have to export this image as an XCF file. In order to be able to retain the "layer mask" information, so it (the layer mask) can be edited when it is reopened in Gimp.
Also, there is no way to export an image with an "unapplied" layer mask and still retain this layer mask information, other then exporting the image as the native Gimp file format of XCF.

If I understand you correctly (I am not acquainted with Photoshop's approach), use "Layer->Transparency->Add Layer Mask" with the Transfer Layer's Alpha Channel option, then disable the mask ("Layer->Mask->Disable Layer Mask"). Your layer's RGB channels will be fully visible and, when you are finished with your editing and ready to export the image, you can apply the layer mask (this step will be automatically performed for most exported formats).