The GARDENA gardening expert
Dear Mr. L., this is pear rust; the same fungi which causes orange-coloured patches and pustules on pear tree leaves. In a certain phase of its development, this fungi parasitizes juniper as its so-called intermediate host. There it forms a slimy mass, just as you have described, and later sends its spores to the pear trees.
Usually, the affected juniper branches should be cut back right into the healthy wood, or removed altogether. The unpleasant thing about this fungal infestation is that it is generally located in the area of the thicker branches or twigs, around the centre of the plant. This means that cutting back will produce holes in the plant. These will grow back over the next few years, but they won't be the most attractive sight until then.
Image: Wacholder: © LianeM - Fotolia.com